An FPSF with 2" foam insulation along the wall and vertically.  2.5" foam insulation at the corners with the following horizontal dimensions:


A = 12"
B = 24"
C = 40"





The rectangle foundation is easy, the polygon shaped foundation will be more challenging.


View model here:


https://3dwarehouse.sketchup.com/model/ab622b36-cc2f-43f8-baa4-f93ceec80741/FPSF

Up until now I have not considered adding insulation but it probably would not be too hard to add in.  I will do more research on FPSF. 

Enabled mod warren webs for the double pitched flat truss configuration:



The truss shown above is an asymmetric double pitched top chord bearing flat truss with a mod warren web configuration and cantilever ends.  That is quite a mouthful.

I have not added the top chord bearing option and the mod warren webs to the other flat truss configurations yet (flat, monopitch, pitched), however I will if specifically requested. There a much hotter items on the plate.

I've seen a lot of great site built trusses.

I actually think a well constructed plywood gusset plated truss with glue and nails will out perform a metal plated truss. It's not the craftsmen that worry me its the DIYer who has limited experience building things and does not take the time and effort to do a quality job.

Trusses are unique structural elements that require special attention to the connection between members (joints).

One method to address the lack of quality control is to overbuild the truss slightly. This method is actually used to some degree in the manufacturer of MPC wood trusses.

I think a lot more people fab their own trusses than we realize.  I don't disapprove but I do think that quality control is imperative.  One bad joint in a truss can cause the entire truss to fail which in turn may cause a catastrophic failure of the roof system.

Some jurisdiction will require an engineer's stamp on any site built trusses, as they should, but there are many situations (ie. agri structures, small buildings) where there is no oversite by a building official or engineer.  For those situations it would be useful to have an easy to use truss calculator that even the lay person could utilize and understand. 

From my side there is some risk and liability associated with this, especially since I have no way to confirm the workmanship of the construction.  If someone were to utilize my calculator and design a truss with plywood gussets, and assuming that they built it per the calculations and input the correct snow loads etc... but the construction was shoddy and it failed would I still be liable?  Probably so.  That is why I have hesitated on releasing the wood gusset portion of my Truss Designer (web based).

@ Fred H

Thank-you for your posting on your recent house project.  People actually using the plugin for "real" work is what makes me think all the hours I have dumped into this aren't totally in vain.

I am interested in these drop-heel trusses you have described.  Please feel free to email me some pictures or drawings, I am not familiar with this configuration but if it something that I'm missing from the plugin I would definitely be interested in adding it in.

Hopefully the plugin made it quicker and easier to generate the roof geometry, that is the intent at least.  I really need to get to work on the wall plugin to round out my plugin family.

I think I've beaten the flat truss to death but I noticed after perusing through a number of flat truss shop drawings that the modified warren is also a popular web configuration.  Its not too big of a deal to enable this configuration.  The flat truss will then have the option between a pratt or mod warren web configuration.

Wood Gusset plates are on my mind this morning (for those of us crazy enough to build or own trusses):



Of course this option would be pretty much useless without the engineering to size the plates and check the fasteners.  I will be giving this some more thought in the near future.

The top chord bearing option is almost complete for the flat trusses.  Here is a preview with a Mansard /w Parapet on the left side and a cantilever on the right side.  The bearing widths can be set independently as can the parapets heights now.



I'm not entirely satisfied with the UI for this truss type, a proper html UI would be much more intuitive but time consuming to create.  Yet another important item on the todo list.

The plugin is starting to stray into some fairly exotic truss territory.

I thought I was done with flat trusses but it was pointed out to me that I also need to consider top chord bearing configurations for this truss type.

I've created a simple matrix below with top and bottom chord bearing flat trusses.  I'm not sure if these make sense, please review and feel free to comment.



The model can be downloaded here:

https://3dwarehouse.sketchup.com/model/acee31ef-9e54-4eca-83d7-02747815ed29/Flat-Truss-End-Details-3

Top chord bearing usually involves the following steps:

1.)  Trimming the heel web up a specific vertical amount (vertical offset).
2.)  Insertion of a secondary heel web next to the trimmed (bearing) heel web.
3.)  Trimming the bottom chord back to the secondary heel web.
4.)  The diagonal web next to the heel is slightly altered by the addition of a secondary heel web.
5.)  Certain configs require an additional heel web on the outside of the trimmed heel web:  Mansard, Cantilever, Mansard w/ Parapet.

I can easily make this all happen and open up the option for top chord bearing flat roof trusses however I want to make sure it is right first.

I've decided to refocus onto the layout portion of the plugin first.  Once I have that functional I will bring the framing and other details into it.  If I can pull this off its going to be really cool.

The flat double pitched truss allows for a user driven asymmetric ridge location as well as differing left and right heel heights.  This opens up virtually any possible truss geometry even a negative pitch if one is so inclined:

The flat truss is the first new truss type added to the plugin in 11 months.  This brings the total number of truss types to approximately twenty two depending on how you classify the variants of the flat truss:



View model here:

https://3dwarehouse.sketchup.com/model/317af74e-a52c-470b-a612-1ba7c06617f0/Medeek-Truss-Yard-4

Here is an example of a small commercial building with a flat truss roof (parapet):



Download model here:

https://3dwarehouse.sketchup.com/model/d8413377-4287-4fb3-99b9-3d200441a2fe/Commercial-Building

Version 1.9.0 - 05.27.2017
- Added flat truss type, configurations: flat, monopitch, pitched.
- Metric input enabled for flat truss types.
- Added gable end trusses for flat truss types.
- Enabled the following end details for all flat truss types: None, Overhang, Cantilever, Mansard, Parapet, Mansard w/ Parapet.



Plates and advanced options are still in progress.  With the amount of configurations available with this truss type it will probably be a while before these next elements are in place.

The flat truss type is very configurable and with a little adjustment of parameters you can also easily create a (non-attic) gambrel truss using the flat pitched option.